The formation and microstructural properties of uniform α-GaOOH particles and their calcination products

• A new synthesis of uniform α-GaOOH particles of different shapes was reported.
• Crystallographic directions and crystal planes in α-GaOOH particles were identified.
• α-GaOOH particles showed differences in crystallite size, thermal and IR properties.
• Uniform α-Ga2O3 and β-Ga2O3 particles were obtained by calcination of α-GaOOH.
• Differences in properties of α-Ga2O3 and β-Ga2O3 samples were observed and discussed.

Uniform α-GaOOH submicron particles of different shapes (spindles, rhombic rods, rhombic prisms, hierarchical particles) were synthesized by simple low-temperature (at 60 °C) or hydrothermal (at 160 °C) precipitation from the mixture of aqueous solutions of gallium(III) chloride and organic alkali tetramethylammonium hydroxide (TMAH) at various pH values (5, 7 or 9). The growth mechanism of these particles was discussed. Crystallographic directions and crystal planes in α-GaOOH particles were identified. Differences in crystallite size, thermal and infrared properties of α-GaOOH particles were observed and discussed. Uniform α-Ga2O3 and β-Ga2O3 particles of the same or similar shapes, containing holes due to dehydroxylation, were obtained by calcination of the corresponding α-GaOOH particles at 500 or 900 °C, respectively. Differences in crystallite size and infrared properties of obtained gallium oxide samples, as well as differences in photoluminescence properties of β-Ga2O3 samples were observed and discussed.